Quantitative histochemical studies of microscopic samples of the cochlea and the cochlear nucleus will be done. Microchemical fluorimetric procedures, low temperature scanning of surface fluorescence, radiometry and GLC-masspectrometry will be used. The peculiarities of energy metabolism, of cyclic nucleotide, and of prostaglandin metabolism will be investigated by comprehensive characterization through direct biochemical analysis of 1. the enzyme patterns, 2. the intermediate levels, and of 3. the rate of product formation of the major pathways. Enzyme activities, metabolite levels and rates of end product formation of the major pathways can be used as indicators of biochemical mechanisms. Simple experimental conditions will be used to decrease and increase the rate of flux through the major pathways by using established pathophysiological (e.g. ischemia, hypoglycemia) and pharmacological measures (e.g. iodoacetate, salicylate, ouabain) and to study the effect of such alterations on the three defined parameters. Based on the knowledge accumulated in the previous stages, experiments will be designed which will assess the influence of deafferentation, of physiological tone stimulation, of noise trauma and of ototoxic drugs on these defined parameters. Studies will be initiated of the biochemistry of development of auditory structures with special reference to susceptibility to priming by noise.